In x-ray analysis systems, high x-ray beam intensity and small beam spot sizes are important to reduce sample exposure times, increase spatial resolution, and consequently, improve the signal-to-background ratio and overall quality of x-ray analysis measurements. In the past, expensive and powerful x-ray sources, such as rotating anode x-ray tubes or synchrotrons, were the only options available to produce high-intensity x-ray beams. Recently, the development of x-ray optic devices has made it possible to collect the diverging radiation from an x-ray source by focusing the x-rays. A combination of x-ray focusing optics and small, low-power x-ray sources can produce x-ray beams with intensities comparable to those achieved with more expensive devices. As a result, systems based on a combination of small, inexpensive x-ray sources, excitation optics, and collection optics have greatly expanded the availability and capabilities of x-ray analysis equipment in, for example, small laboratories and in the field.
Monochromatization of x-ray beams in the excitation and/or detection paths is also useful, as discussed above. One existing x-ray monochromatization technology is based on diffraction of x-rays on optical crystals, for example, germanium (Ge) or silicon (Si) crystals. Curved crystals can provide deflection of diverging radiation from an x-ray source onto a target, as well as providing monochromatization of photons reaching the target. Two common types of curved crystals are known as singly-curved crystals and doubly-curved crystals (DCCs). Using what is known in the art as Rowland circle geometry, singly-curved crystals provide focusing in two dimensions, leaving x-ray radiation unfocused in the third or orthogonal plane. Doubly-curved crystals provide focusing of x-rays from the source to a point target in all three dimensions. This three-dimensional focusing is referred to in the art as “point-to-point” focusing.
Commonly-assigned U.S. Pat. Nos. 6,285,506 and 7,035,374 disclose various configurations of curved x-ray optics for x-ray focusing and monochromatization. In general, these patents disclose a flexible layer of material (e.g., Si) formed into curved optic elements. The monochromating function, and the transmission efficiency of the optic are determined by the crystal structure of the optic. The present invention provides certain improvements in the formation of curved crystal optics, offering important performance advantages.